Attempts to detect open fractures and non-sealing faults with dipmeter logs

Abstract

Abstract If enough stress-generated breakouts have been identified on four-arm dipmeter logs to map regional horizontal stress trajectories, it may be possible to use anomalous orientations to identify open fractures and non-sealing faults. These act as free surfaces and, if they were oriented obliquely to regional stresses, deflect them locally. This type of analysis is simple to apply and appears to offer a novel way to obtain key information required for optimizing the production of oil and gas. In offshore eastern Canada, the regional stress regime is well established and local deflections appear to be caused by near-by open fractures and non-sealing faults. In the Aquitaine Basin in France the regional stress signature is not homogeneous. Though some anomalous orientations appear to be caused by open fractures and faults, it is clear that many are not. Hence the method may not be applicable everywhere. Possible reasons include differences in the σ H :σ h ratios of the two areas and the geotectonic settings.